Abrasive article and manufacture



Dec. 7, 1943. -A. 1.. BALL EI'AL ABRASIVE ARTICLE AND MANUFACTURE Filed Nov. 24, 1941 hum-01 6 45527" L. 501.1. BnYMa/vo J j EOM/E L (751. Tan

- strips.

Patented Dec. 7, 1943 UNITED STATES PATENT. OFFICE i p I 2,335,902 l Anrmsrva narrow AND MANUFACTURE 1 Albert L. Ball, Iiewiston, and Raymond C. Benner and Romie L. Melton, Niagara Falls, N.'Y., as-

signors to The Carborundnm Company, Niagara Falls, N. Y., a corporation, of Delaware Application November 24, 1941', Serial No. 420,206

13 Claims.

This invention relates to abrasive articles and methods for their manufacture. More particularly,.it relates to flexible or resilient abrasive articles having a mild or soft abrad'ing action,'

and formed of a series of convoluted felted, fibrous strips having abrasive grain and adhesive therefor included internally of the individual The invention especially pertains to abrasives made from one or more flexible, fibrous abrasive-containing strips which are arranged in convolutions and secured together in convoluted position with or without suitable flexible backings to form various abrading devices, such as 1 grinding and polishing wheels, flexible abra sive discs, sanding and polishing belts, blocks, pads and other shapes which provide a relatively resilient or soft abrasive action.

, The invention is well adapted to the provision of relatively flexible grinding and polishing wheels, and also to flexible-backed abrasive articles such as abrasive belts, discs and the like, and will be described largely as it pertains thereto. However, many other resilient types of abrasive articles which provide a "soft" grinding action for numerous grinding purposes can be made in a similar manner. The invention provides a means of making such belts, discs and the like with an abrading portion of substantial thickness and. therefore longer life with a retention of the requisite flexibility or pliability for satisfactory operation.

Abrasive discs and'belts commonly in use are composed of a flexible backing material to which a prolonged period of use such as might be ex- 'pected only from similar type articles provided with a multiple-layered abrading surface.

In accordance with the present invention, improved abrasive articles of the resilent type are made by a process which consists of two sequent steps or procedures. The first step is that of forming a satisfactory felted fibrous web material containing abrasive particles included internally thereof and retained by an adhesive .binderalso included therein. The abrasive and adhesive content of the fibrous material is incorporated and distributed through the fibrous web abrasive articles of the present invention. The

previously-formed abrasive-containing fibrous web is cut or slit into strips of a required width and length which are then arranged in a series of convolutions and either adhesively secured together in convoluted form or adhesively attached the abrasive articles and methods of manufacis attached a single layer of abrasive particles by means of an adhesive coating on the backing. This thin abrading layer of abrasive grains quickly becomes loaded during grinding or polishing operations and tends to inhibit or interfere with the cutting action of the abrasive grain. Furthermore the essentially single layer of abrasive applied to the belt or disc backing tends to efiectively limit the usefulness of such products to a comparatively short period of time. Efforts to apply multiple layers of abrasive grain to the backings by repeated coatings ofabrasive and adhesive have been unsatisfactory due to lowering of the flexibility or pliability of the article, making it too stifi and rigid for'use. Abrasive wheels of substantial thickness have also been lacking in lateral play or pliability and are hard and rigid in character.

ture, reference is made to the accompanying drawing showing specific examples of such products, and in which: a

Figure 1' shows a plan view'of an abrasive wheel embodying the presentinvention and formed from a long narrow strip of abrasive-containing fibrous web material tightly wound upona bushhesively attaching a spirally convoluted abrasivestrip material to a, flexible backing;

'The present invention provides for the first time, abrasive belts, discs and like articles producing a cool, free grinding or polishing action Figure 4 shows a diametrical cross-section through the disc of Figure 3;

Figure 5 shows as a further embodiment of the present invention a top plan view of a representativefragment of an abrasive belt formed by a convoluted strip material adhesively attached to a flexible backing, the convolutions being in this case a series of transverse folds of the strip 7 material extending substantially across the width of the flexible backing; and

Figure 6 is a vertical cross-section through the embodiment of Figure 5..

The abrasive-containing fibrousweb material used in making the products ofthe present invention can be manufactured in several ways. A very satisfactory method of making included abrasive sheet material of the herein required type is that set forth and fully described in copending application Serial No. 375,514, filed J anuary 22, 1941. Briefly, the felted fibrous web is I formed by feeding a plurality of thin carded fibrous'membranes from a number of carding assemblies onto a moving endless support so that each membrane is deposited or superimposed upon the preceding membranes until a web of loosely felted fibrous material of the desired thickness is built up on the traveling support. A number of abrasive grain hoppers are also disposed between the carding assemblies and above the traveling conveyor. Abrasive grain is fed from the hoppers onto the fibrous membranes at various stages in the building up of the final web, so that, as a result, the abrasive material is applied between the individual membranes making up the web and so is internally distributed throughout the fibrous web or sheet. A suitable adhesive binder is then incorporated within the fibrous-abrasive web, the web consolidated to a desired density and the web passed to a curing zone, where the adhesive is matured or set. The included abrasive web is then wound into rolls for use as an intermediate product or source for the manufacture of the products herein described.

In practising the invention, any of the abrasive materials in common use may be employed, such as silicon carbide, diamonds, boron carbide, fused aluminum oxide, fiint, corundum, emery, rouge and similar substances. The size of the abrasive particles may vary from the finest polishing or bufiing powders to the coarser grit sizes used in grinding.

Other methods of incorporating abrasive material internally of the fibrous sheet material during its manufacture may be employed. For example, the abrasive particles can be thoroughly admixed with the adhesive binder and the mixture applied to the web by the usual adhesiveapplying rolls. This method has been found to be particularly satisfactory for the inclusion of the finer abrasive materials of the size empl y in buffing and polishing operations.

Another method is to project the abrasive material into the web or sheet after it has been built up to the desired thickness and immediately prior to consolidating the web. The projection of grain the strength and eliminate any laminations from the web. For a more complete description of the process, reference is made to copending applications Serial Nos. 375,516 and 375,517, filed January 22, 1941, in which further details are also given of the above procedures for including abrasive material within the fibrous structures.

The felted fibrous abrasive-containing sheet material made as above described constitutes the raw material used for the making of abrasive articles in accordance with the present invention. The fibrous abrasive sheeting is cut or slit into strips of the desired width and length and these strips are arranged in convolut.'.ons and secured together with or without suitable flexible backings to form numerous types of abrasive articles such as are hereinset forth. Th various drawings, in which like numerals in the different figures refer to similar parts, are illustrative.

Referring to the detailed drawing, Figures 1 and 2 depict a finished grinding wheel made in accordance with the teachings of the present invention. The wheel consists of a central bushing I composed of a metal, wood, plastic or any other suitable, rigid material about which a long, narrow strip 8 of felted, fibrous abrasive-containing material has been tightly wound in a series of spiral convolutions and which is held in convoluted position by means of an adhesive between the successive convolutions.

One method of manufacturing a grinding Wheel such as shown in Figures 1 and 2 is as follows: A suitable bushing of the desired size is placed upon a spindle or shaft and a strip of felted, fibrous material having abrasive and adhesive included within the strip, the width of which is sufficient to produce an abrasive wheel of desired thickness, is fed under tension onto the revolving spindle until sufiicient strip material has been fed onto the spindle to build up a wheel diameter of the desired size. Immediately prior to being wound upon the spindle or bushing the strip material is fed between a pair of squeeze rolls, one of which is partially immersed in a pan of adhesive, in order to apply a thin film of adhesive between the successive convolutions of the strip. The adhesiv may b applied by other means such as spraying or brushing it onto the strip. However, this step of applying a secondary adhesive can be omitted entirely if desired and the final retention of the strip in conis suitably carried out by means of a blast of air or gas against one or both surfaces of the fibrous web, the air stream being laden with the abrasive material to be included internally of the web. The other steps in the formation and consolidation of the web are carried out in a manner similar to that used in the previous procedures.

Felted fibrous webs having abrasive material included within the web and which are suitable for use in the fabrication of the herein described products can also be made by a modification of the above processes in which the individual fibers are interwoven and interlocked by a gentle air or aseous agitation of the thin carded membranes during their deposition. This process is termed aerodynamic weaving" and is used to promote voluted form accomplished by means of the primary adhesive content of the fibrous strip material placed therein at the time of making the abrasive sheet material. After the wheel has been built up to the desired diameter it is removed from the spindle, placed in a suitable mold and subjected to a temperature and pressure sufficient to mature or. cure the adhesiv and thereby retain the convoluted strip material in permanent spirally wound position.

It has been found that various adhesives generally employed in the manufacture of abrasivecontaining fibrous materials are satisfactory for use as primary adhesives internally of the strip material and also as the secondary adhesivefor combining and holding the strip material in position. When a secondary adhesive is used it can be the same as or-difierent from the adhesive employed in making the strip material; by various combinations of the adhesives specific properties and characteristics such as varying degrees of rigidly or flexibility may be imparted to the abrasive article as desired. Highly satisresins such as phenol formaldehyde resins, urea resins, and the like, casein, rubber and latex cements, sodium silicate, shellac,,magnesium oxychloride cements and the like.

Obviously the pressure and temperature employed in the final forming operation will depend upon the particular adhesivebeing used. With a plasticized animal glue satisfactory selfbonding results. have been obtained by using a glue of total solids 30-40%.- For example, a wheel one half inch. thick and eight inches diameter is matured by placing it in a hot press under low pressure and applying a steam pressure of 60 pounds and a temperature of 300 F. for a period of 30 minutes.

Figures 3 and 4 show an abrasive disc in which a narrow strip 9, approximately one quarter of an inch in width, of felted fibrous abrasive material has been spirally wound or convoluted and adhesively attached at one edge to a flexible backing Ill by means of a layer of suitable adhesive I4. The flexible backing i is provided with a centrally located arbor ii for mounting upon the shaft of-a grinding or polishing machine. Hyd'rolyzed fiber backings have been found to provide the essential balance betweenv stiffness and flexibility to produce satisfactory grinding results. Other backing materials of the requisite strength and pliable character may be used, as for example, combinations of paper and cloth, flexible metals and the like. The particular embodiment illustrated in Figures 3 and 4 is a disc in which the abrasive strip material is closely spiralled to'provide a relatively solid or continuous polishing surface although by reason of the strips being adhesively secured only at their lower edges adjacent the backing or support they are allowed to move laterally to a sufficient degree to permit a close following of the contour of the work being finished and also provide a resiliency or softness of action not otherwise obtained.

Figures 5 and 6 illustrate a' fragmentary view of an abrasive belt in accordance with the teachings of the invention-and made in a manner similar to the disc shown in Figures 3 and 4..

However in fabricating an abrasive belt of the type shown the convolutions of strip material take the form of transverse folds l2 of the strip material folded back and forth across the 080k.- ing I3 and extending substantially across the entire width of the backing. Lengths of belting so made are joined to form endless belts and other products by splicing the backing by any of the well known means (not shown) such asbev-- eled Joints, 'butt joints or overlapping joints, etc. One of the advantages of such an endless belt embodying the present invention is the fact that such splices are confined to the backing and by not extending into the abrading portion are so as to provide a substantially continuous abrading surface l5.

Various modifications may be made in the ar- 1510188 illustrated without departing from the spirit of the invention.

For instance the grinding or polishing surface I5 of belts, discs and the like may be given added pliability and flexibility and an even softer abrasive action by providing a discontinuous surface. This can be done by spacing the successive convolutions or folds of strip material slightly apart so as to provide a clearance space between adjoining convolutions/ end is to alternate the strip material shown with an interleaving strip of material of lesser height,

which interleaving material may be the same abrasive-included fibrous strip material slit to a narrower width or it may be some inexpensive material chosen for specific properties of its own.

It has been found that the character of theabrasive articles produced by the herein-de-.

scribedprocess can also be altered to any desired degree by variations in the quantity and character of the adhesive binder employed in making able adhesive binders for making the includedabrasive strip material for the aforesaid articles that the adhesive substance does not smear during grinding operations. This is especially true in the case of polishing wheels and. devices where smearing of the bond tends to produce a.hot

cutting or burning action which is ruinous to the finish being produced.

Among those substances which can be satisfactorily used as bonding materials. herein and which are non-smearing, are included glue adhesives, particularly when treated with plasticizing agents such as ethylene glycol, dibutyl plithalate, glycerine and the like. The plasticizer may amount to as much as 40% by weight of the total adhesive binder. Other non-smearing adhesives which can be, used are vulcanized latex, casein glues, shellac, sodium silicate, magnesium oxychloride, various rubber cements, urea resins, phenol-formaldehyde resins and various other resm adhesives having similar properties.

Having described and setforth the invention in detail, the-scope of the invention is not to be confined other than by the appended claims:

We claim:

, 1. An abrasive article comprising a series of convolutions of thin felted strip of fibrous textile material having substantially all the abrasive strip of fibrous textile material having substan-- tially all theabrasive particles and adhesive therefore included internally of the fibrous strip,

said abrasive-containing strip material being ad- Another manner of achieving the same,

hesively attached at one edge to a suitable backing support.

4. An abrasive wheel comprising a compacted series of closely wound circular convolutions of thin felted trip of fibrous textile material havrial having substantially all the abrasive particles and adhesive bond included internally throughout the fibrous strip.

6. An abrasive article comprising .a flexible backing having a plurality of narrow strips of thin felted, fibrous textile abrasive-containing material adhesively secured to the surface thereof, substantially all the abrasive material being dispersed internally throughout the fibrous strip -material, said strips being secured to the backing at one edge of the strips and extending outwardly from the backing, successive convolutions of said strip material being paced slightly one from the other to impart added flexibility to the abrading action of the article.

'I. A flexible abrasive article comprising a series of convolutions of thin felted strip of fibrous textile material having substantially all the abrasive particles and an adhesive binder included internally throughout said fibrous strip material, said strip material being held in its convoluted position by reason of its being adhesively secured at one of its edges to a flexible backing.

8. A flexible abrasive article comprising a series of slightly spaced convolutions of thin felted strip of fibrous textile material. having substantially all the abrasive particles and an adhesive binder included internally throughout the fibrous strip material, the spaces between successive convolutions being filled by an additional strip material having a width substantially less than that of the aforesaid abrasive strip material, said strip material being held in its convoluted position by means of its being adhesively secured at one of its edges to a flexible backing.

9. The method of manufacturing abrasive articles from a felted, fibrous textile sheet material having substantially all the abrasive particles and an adhesive binder included intemally of the sheet material which comprises slitting said sheet material to form long narrow strips of the desired width, winding the narrow strip material in spiral convolutions about a mandrel to form a wheel of the desired diameter and applying heat and pressure to the convoluted material to cure the adhesive content and unite to form an abrasive article therefrom.

10. The method of manufacturing abrasive articles from a felted, fibrous textile sheet material having substantially all the abrasive particles and an adhesive binder included internally thereof which comprises slitting said sheet material to form long narrow strips of the desired width, winding the narrow strip material in spiral convolutions about a mandrel to form a wheel of the desired diameter, introducing a secondary adhesive between successive convolutions of the strip material, and applying heat and pressure to the convoluted material to cure the adhesive and unite to form an abrasive article therefrom.

11. The method of manufacturing abrasive articles from a felted, fibrous textile sheet material having substantially all the abrasive particles and an adhesive binder included internally thereof which comprises slitting said sheet material to form long, narrow strips of the desired width, assembling said strip material in convolutions, applying adhesive between successive convolutions to retain the strip material in convoluted position and applying heat to cure the adhesive anc unite and form an abrasive article therefrom.

12. The method of manufacturing abrasive articles from a felted, fibrous textile sheet material having substantially all the abrasive particles and an adhesive binder included internally thereof which comprises slitting said sheet material to form long, narrow strips of the desired width, assembling said strip material in convolutions, and applying heat and pressure to cure the adhesive binder content and thereby retain a the material in its convoluted position and form ALBERT 1. BALL. RAYMOND c. BENNER. ROMIE L. MELTON. 

